How to Wear a Tie Clip: Placement, Width and Fit
A tie clip keeps the tie from swinging forward when you lean over a desk or sit down to eat. Its grip should catch both tie blades and the shirt placket.
Start between the third and fourth shirt buttons, counting the collar button first. Check it again with your jacket fastened. A small adjustment may be needed to keep the clip visible without sitting high on the chest.
Pick the width to match the tie

Use a clip shorter than the tie where it crosses it. Roughly half to three-quarters of the tie width is a useful starting range. A narrow tie will usually need a smaller bar.
Let the tie move naturally
Give the fabric a little slack above the clip so it doesn’t pull at the collar when you move. You can usually skip the clip with a waistcoat, which already holds the tie in place.